Liquid cooled ozone generator

ABSTRACT

An ozone generator module of the electirc discharge field type is provided having at least one cell comprising an assembly of three concentric tubular members, the inner and outer tubular members being electrodes separated by a tubular dielectric member spaced from one of the electrodes a distance sufficient to define a high density electric discharge zone between them, the cell or cells being disposed within a liquid container. Substantially optimum conditions for the production of ozone are provided by making the cross sectional dimension of the field uniform throughout to within a very small range of tolerance and by controlling the temperature of the electrodes by cooling them with liquid coolants one of which is a dielectric liquid, and limiting the density of the field by regulating the voltage across the field and the frequency employed.

ijite wieS ollylty 1 Oct. 16, 1973 LIQUID COOLED OZONE GENERATOR [75]Inventor: Joseph Bollyky, Stamford, Conn. [73] Assignee: PollutionControl Industries, Inc., Stamford, Conn.

[22] Filed: Sept. 22, 1971 [21] Appl. No.: 182,681

[52] US. Cl 204/321, 204/176, 204/320 [51] Int. Cl. C01b 13/10, COlb13/12 [5 8] Field of Search 204/321, 313-320, 204/322 [56] Eeferencescited UNITED STATES PATENTS 574,341 12/1896 Pridham 204/321 1,316,3429/1919 Walden 204/321 3,364,129 1/1968 Cremer et al.... 204/3213,551,321 12/1970 Guillerd 204/321 Primary Examiner-F. C. EdmundsonAtt0rney.lohn W. Hoag An ozone ABSTRACT generator module of the electircdischarge field type is provided having at least one cell comprising anassembly of three concentric tubular members, the inner and outertubular members being electrodes separated by a tubular dielectricmember spaced from one of the electrodes a distance sufficient to definea high density electric discharge zone between them, the

cell or cel ls being disposed within a liquid container.

M Substantially optimum conditions for the production of ozone areprovided by making the cross sectional dimension very small of the fielduniform throughout to within a range of tolerance and by controlling thetemperature of the electrodes by cooling them with liquid coolants oneof which is a dielectric liquid, and limiting the density of the fieldby regulating the voltage across the field and the frequency employed.

4 Claims, 6 Drawing Figures Patented Oct. 16, 1973 3 Sheets-Sheet R 6 eg mu rv am HL 7 H 0V 0M 5 Mr.

SILICONE OIL 01/ 7' Patented Oct. 16, W73 3,766,051

mom r//v VJ v/u v 55 6 IND/CH MR commons? oooooooo ER LIQUID COOLEDOZONE GENERATOR FIELD OF THE INVENTION This invention relates to anozone generator module and particularly to one of tubular form.

Ozone generators of the prior art have been very inefficient in theproduction of ozone relative to the size of the electrode surfacesemployed, ane this has been true whether air or pure oxygen has been fedinto the ozone producing field. The size and cost of equipment hastherefore been high. When pure oxygen was employed instead of air theozone output was twice as high as from air, but the cost of operationwas greatly increased because of the cost of oxygen.

It is accordingly an object of this invention to substantially increasethe production of ozone relative to the size of the electrode surfacesemployed.

Another object of the invention is to provide apparatus and controls forits operation by which a very pronounced increase in the production ofozone relative to the size of the electrode surfaces may be obtainedusing air, or a mixture of air and oxygen, or a mixture of nitrogen andoxygen in which up to 65 percent of nitrogen is present.

A further object of the invention is to provide within a compactgenerating device a module a maximum of electrode surface which ispractical from the point of view of cost of equipment.

SUMMARY OF THE DISCLOSURE The terms cell" and ozone producing cell areused herein to indicate a combination of three tubular members includingtwo electrodes separated by a dielectric tube. One of the electrodes isa metal coating on one face of the dielectric tube.

The term module is used herein to mean one or more ozone producing cellsdisposed in a liquid container and connected within the same electriccircuit.

The terms air gap and ozone producing space are used hereininterchangeably.

In accordance with this invention one or more, preferably several, ozoneproducing units or cells are enclosed within a non-conductive liquidcontainer thereby providing an ozone generator module. Two or moremodules may be joined together, if desired, to form an ozone generatorof increased capacity. In the preferred form of the structure shown inFIGS. 1, 2 and 3 each cell comprises a metal tube surrounded and spacedradially from a tube made of suitable dielectric material, such asglass, the outer surface of which is coated with metal. The metal tube(first electrode) and the metal coating (second electrode) are connectedin an electric circuit to produce between them a high density electricdischarge field. Gas comprising oxygen is caused to travel continuouslythrough the space surrounding the metal tube, between the metal tube andthe uncoated surface of the tube of dielectric material. A flow ofcooling liquid which may be water is provided through the metal tube,and a flow of cooling dielectric liquid, which desirably may be siliconeoil, is provided over the metal coating on the dielectric tube or tubeswithin the liquid container. For a module comprising two or more cellsheaders are provided for simultaneously supplying cooling liquid and gascomprising oxygen to each of the cells, and other headers are providedinto which the cooling liquid and the gas comprising oxygen aresimultaneously discharged from each of the cells.

Preferably the cooling agents are flowed counter current to the air ofother feed gas comprising oxygen.

The distance across the electric discharge field is controlled bycareful positioning and machining of the field defining tubes to madethis distance uniform throughout the extent of the field to a toleranceon the order ofi 0.017 of an inch or less.

The temperature of the electrode surfaces is carefully controlled tomaintain them preferably at a temperature on the order of 1 10 F. orless, by means of the liquid coolants and by controlling the power inputof the field at a level which will permit the cooling liquids tomaintain the temperature of the electrode surfaces as stated above. Ihave found that for accomplishing this result the power input employedshould have an upper limit of 5,000 watts per square foot of electrodearea, and that if this limit is exceeded the coolants cannot cool theelectrodes sufficiently. I have found that the power input can becontrolled within the upper limit of 5,000 watts per square foot ofelectrode area by limiting the voltage to within a range having 25,000volts (RMS) as its upper limit and controlling the frequency employed towithin a range having 5,000 cycles per second as its upper limit.

The invention will be best understood by reading the followingdescription in connection with the drawings in which,

FIG. 1 is a cross sectional view showing a module comprising a singleozone producing cell within a liquid container;

FIG. 2 is a cross section taken on the line l1 of FIG. 3 showing seventubular ozone generating cells disposed in spaced parallel relationwithin a cylindrical liquid container;

FIG. 3 is a vertical sectional view of an embodiment of the inventionshowing cooling liquid and air headers disposed at either end of thebody portion of the generator shown in FIG. 2, with cooling liquid andair inlets and outlets for the respective pairs of headers, and withinlet and outlet means for the liquid container body portion; this viewis partially cutaway to show in detail one generating unit or cellwithin the said surroundingliquid container and its connections with theheaders;

FIG. 4 is a cross section taken on the line 4--4 of FIG. 5 showing amodification of the invention in which the position of the metal tubeand the metal coating'on one side of the dielectric tube are reversedwith respect to the dielectric tube, the metal tube (first electrode)being the outer one of the three concentric tubular members and themetal coating (second. electrode) being on the inside surface of thedielectric tube, and the air gap being between the outer uncoated faceof the dielectric tube and the surrounding metal tube;

FIG. 5 is a vertical sectional view partly cut away of the embodiment ofthe invention shown in FIG. 4, and

FIG. 6 is a schematic view showing a plurality of modules associatedtogether to provide an increased volume of ozone each module beingprovided with an indicator-controller which will isolate the module ifthere is failure of the dielectric tube of any cell of the module.

DESCRIPTION electrically non-conductive liquid container 16 andsurrounded by liquid therein. Desirably the liquid container may be madeof any suitable plastic such for example as polyvinyl chloride.

In FIG. 2 and 3 a number of ozone producing cells are shown assembledwithin a liquid container 16, the cells being spaced sufficiently sothat each of the cells is surrounded by liquid. The ozone producingcells shown in FIGS. 1, 2 and 3 each comprises a grounded metal tube 10,which may desirably be made of stainless steel, and is a first electrodewhich is spaced from, and surrounded by, a concentric tubular member 12made of dielectric material, such for example as glass, the outer faceof the dielectric tube having thereon a coating of metal 14 which is asecond tubular electrode.

In the single cell embodiment of the invention shown in FIG. 1 the innermetal tube is connected through ground to one end of the secondary 18 ofa power transformer and the metal coating 14 on the outer surface of thedielectric tube is connected to the other end of the transformersecondary. The primary coil 20 of the transformer is connected to asource of high frequency and high voltage power supply, not shown, sothat a high density electric discharge field can be provided within eachair gap 13. When the electric circuit is energized a high densityelectric field will be created in the air gap 13 between the inner metalelectrode 10 and the surrounding, concentric dielectric tube 12.

In the multiple cell modules of the kind illustrated in FIG. 2 and 3 theelectric circuits through the air gaps 13 of these cells are completedby connecting the metal coating 14 of the center cell directly to thesecondary of the transformer and connecting the metal coating 14 of theother cells to the metal coating 14 of the center cell by leads 19.

The function of the liquid container 16 is to maintain a body of coolingliquid in contact with the outer metal coating 14 on each tube 12comprising the cell or cells. The liquid container 16 is provided withthe liquid inlet 22 adjacent one end and with a liquid outlet 24adjacent its other end so that a flow of cooling liquid can be providedthrough the space within it.

For multi-cell modules air and liquid coolant headers are provided atboth ends of the cells for simultaneously supplying air into, andexhausting it from, the electric discharge zones or air gaps of all ofthe cells, and for simultaneously supplying cooling liquid into, andexhausting it from the inner tubular member of all of the cells.

An air supply header 26 having the inlet port 28 extends over the upperend of the cells and also extends over the upper end of the side wall ofthe liquid container l6 and forms the top of the liquid container. Anair exhaust header 32, having the inlet port 34 extends over the lowerends of the cells and over the lower end of the liquid container sidewall and forms the bottom of the liquid container. The air supply header26 communicates with the air gaps 13 of all of the cells through theannular air ports 30 respectively, and similarly the air gaps of all ofthe cells communicate with the air discharge header 32 through theannular ports 36 respectively.

A cooling liquid supply header 38 having an inlet port 39 is disposedbelow the air discharge header, and cooling liquid discharge header 42having the outlet port 44 is disposed above the air supply header 26,and

conduits 40 extend from the liquid supply header 38 through the airdischarge header 32 longitudinally and through each of the tubes 10 andthrough the air supply header 26 into communication with the coolingliquid discharge header 42. Each conduit 40 has two sets of ports p, popening into tubes 10 adjacent their respective ends.

In the multi-cell generator illustrated in FIG. 2 herein sevengenerating units are shown each comprising an inner metal tube 10surrounded by a dielectric tube 12 having an outer facing of metal 14,and all seven of these units are shown surrounded by a tubular liquidcontainer member 16. The units are spaced apart within the container 16and the outer metal coated faces 14 of tubes 12 are all contacted by acooling dielectric liquid such as silicone oil which is continuouslycirculated through tube 16 from an inlet port such as 22 shown in FIG. 3to an outlet port such as 24. The dielectric liquid employed may becooled as by a coil (not shown) of cold water while being circulated. Itwill be noted that the provision of a tubular liquid containersurrounding one or several cells not only provides for cooling theentire electrode surface 14 of a single ozone producing cell, or theouter surfaces 14 of several ozone producing cells, but also conservesspace so that the entire generator will be compact as well as efficient.In a multiple cell module from five to nine cells are preferred as acompromise between maximum electrode surface and the cost of the cells.I have found that while the addition of cells provides increasedelectrode surface the corresponding increase in efficiency begins todiminish when this number of cells is exceeded and the increase in costmakes the use of a greater number of cells impractical.

In FIGS. 4 and 5 the position of the electrodes in the tubular assemblycomprising each cell is reversed. The outer electrode is a groundedmetal tube 50, and the inner electrode is a metal coating 54 on theinner surface of the dielectric tubular member 52. The electricdischarge field or air gap of each cell, into which the ozone producinggas is fed, is defined between the dielectric tube 52 and thesurrounding, radially spaced metal tube 50. The transformer secondary isconnected by lead 53 directly to the metal coating electrode 54 of eachcell and the circuit through the air gap 56 of each cell is completedfrom the metal tubular electrode 50 through ground.

In a multi-cell module the transformer secondary is connected to themetal coating electrode 54 of one cell and this electrode is connectedto the similar electrodes of each of the other cells by leads 55.

The other parts of the structure shown in FIGS. 4 and 5 may be the sameas those shown in FIGS. 1 and 2 and like numerals are used to identifylike parts. It will be understood that in this embodiment a dielectricliquid is supplied into the header 38 instead of water, to flow over themetal coatings 54 and that water may be circulated through the liquidcontainer 16 instead of dielectric liquid. The supply and circulation offeed gas through the ozone producing air gaps will remain the same.

In FIG. 6 a plural number of modules are shown combined to provide agenerator of greater power. Although the chance of breakdown of a cellin my device is greatly reduced due to the uniformity of the crosssectional dimension of the electric discharge field and the efficientcooling, it is desirable whether using a single module or a pluralmodule generator to connect in the circuit of each module anindicator-controller 58 which may be of known kind to monitor thecurrent drawn by the module, and to control the isolating valves V andshut off the flow of gas comprising oxygen into and out of the electricdischarge space, and also the flow of dielectric coolant, in case ofpuncture or failure of the dielectric tube that leads to a high currentstage.

An important factor in the success of my invention is that I control thedistance across the discharge field to within a tolerance of: 0.017 ofan inch or less. This is accomplished by careful machining of theopposed surfaces defining the air gap and results in substantiallyavoiding puncture of the dielectric tube and providing a substantiallytrouble free structure and producing, along with temperature control, acondition which approaches the optimum as much as is practical keepingin mind the production expense of the equipment. It should be noted thatwithout precision machining and using a standard metal tube and astandard 100 millimeter pyrex glass dielectric tube the air gapcomprising the electric discharge field would have a tolerance of i0.073 inches or more.

dry air. So far as I know the most nearly comparable production of ozoneby prior art apparatus and methods has been a production of from 3 to 6grams of ozone per square foot of electrode surface per hour from dryair F. dew point), and from 5 to 20 grams of ozone per square foot ofelectrode surface per hour from dry oxygen. It will be noted that inthis comparison the production of ozone per square foot of electrodearea per hour is more than eight times the prior art production usingdry air.

The following three tables denominated as EXAM- PLE 1, EXAMPLE 2 andEXAMPLE 3, each cornprises several experiments made with the apparatusdis closed herein using feed gas made up of various percentages of acombination of pure oxygen and dry air assumed to contain 80 percentnitrogen. These examples show that although with prior art ozonatorswhen nitrogen was present in the feed gas in excess of 10 percent therewas a drastic falling off in the amount of ozone produced this is notthe case when using the apparatus and method taught herein; the ozoneoutput per square foot of electrode area is astonishingly andunexpectedly high; and a surprisingly high conversion of feed gas toozone is achieved.

Feed gas Power input Ozone output 02 (wt. N2 (wt. Flow Pressure VoltsFrequency Power 0; (g. hr.) 03 (wt. Efliciency percent) percent)(s.e.f.h.) (p.s.i.g.) (RMS) (Hz) (watts) (sq. ft.) percent) (kwhJlb.oz.)

I have found that in ofder to obtain the suprisingly good resultsobtained in the operation of my device it is not only important tocontrol the tolerance of the air gap to within i 0.017 of an inch butalso to maintain the temperature within the discharge field at not morethan 110 F. I have realized this temperature by using liquid coolants tocool the electrodes and controlling the power density of the electricdischarge field by keeping the power input to within a range having5,000 watts per square foot of electrode surface area as its upperlimit. Using water as one of the cooling liquids and using a dielectricliquid which is recycled and cooled with water as the other coolant, theliquid coolants cannot sufficiently reduce the temperature of theelectrodes to provide a temperature of 110 F. or less in the electricdischarge zone if a wattage in excess of 5,000 per square foot ofelectrode area is employed.

While the wattage is a function of the voltage across the dischargefield and the frequency employed I have found that best results areobtained by controlling the voltage to within a range up to 25,000 volts(RMS) and the frequency to within a range up to 5,000 cycles per second.

I have found that ozone generators made and operated as taught hereinproduce ozone, either from the air or other gas comprising oxygen orfrom pure oxygen, with an efficiency never heretofore attained and whichis truly surprising. With an oxony generator made and operated accordingto this invention I have produced in excess of 50 grams of ozone persquare foot of electrode area per hour from 40 F. dew point Theexperiments of EXAMPI QE I show that the ozone output, conversion andefficiency of the ozonator of this invention do not change substantiallywhen the composition of feed gas is varied within a range of frompercent oxygen to a 35 percent oxygen- 65 percent nitrogen mixture. Incontrast, prior art ozonators suffer substantial and increasing loss ofefficiency as the nitrogen content in the oxygen-nitrogen feed exceeds10 percent. See for example W. E. Cromwell and T. C. Manley, Effect ofGaseous Diluents on Energy Yield of Ozone Generation from Oxygen", OzoneChemistry and Technology Advances in Chemistry Series, No. 21, page 310,American Chemical Society, Washington, D. C., 1959, and curve reproducedbelow.

M iv 7 v 7 727"" TV V 7 I Feed gas Power input Ozone output Oz (Wt. N2(wt. Flow Pressure Volts Frequency Power 03 (8. hr.) (wt. Efiicioncypercent) percent) (s.c.f.h.) (p.s.i.g.) (RMS) (Hz.) (watts) (sq. ft.percent) (kwh./lb. oz.)

20 (air)- (80) 856 15 12, 000 2, 000 1, 500 52 0. 7 8. 2 20 (air) (80)428 15 12, 000 1,800 1, 800 47 0.53 10. 5 100 0 128 9, 300 2, 100 2, 10043 1. 6 4. 8

Gh MPL ET;

bular electrodes connected in a high frequency electric 0 circuit andseparated by a concentrically disposed dielectric tube, the dielectrictube being spaced from one of the said tubular electrodes providing anelectric discharge zone, the distance between the tubes defining thedischarge zone being uniform to within a tolerance of: 0.017 of an inchthroughout the said zone, means for flowing a gas comprising oxygenthrough the discharge zone, means for flowing a liquid coolant throughsaid liquid container against a face of one of said electrodes, andmeans for flowing a liquid coolant Feed gas Power input Ozone output 02(wt. NZ (wt. Flow Pressure Volts Frequency Power 03 (g. hr. 0 (wt.Eificiency percent) percent) (s.c.f.h.) (p.s.i.g.) (RMS) (Hz (watts)(sq. ft.- percent) (kwhJlb. oz.)

0 33. 8 12 10, 400 2, 100 750 33. 5 5. 7 6. 2 43. 2 12 10, 400 2, 100750 36. 7 4. 1 5. 7 36 20. 3 12 10, 400 2, 100 750 26. 0 6. 2 8. 0 6575. 5 12 10, 400 2, 100 750 35. 0 2. 2 5. 9 20 (air) 80 122. 0 12 10,000 2,000 1, 050 31. 3 1. 3 9. 2

In contrast to the exceptionally high conversion of feed gas to ozoneshown above prior art ozonators could produce up to one per centconversion from air and up to two per cent conversion from pure oxygen.See Ozone Chemistry and Technology, Advances in Chemistry Series, No.21, pp. 304-306, American Chemical Society, Washington, D. C., 1959 andU.S. Pat. No. 2,822,317.

A measure of the unexpectedness of the results achieved by my apparatusand method of operation is the fact that they are achieved using arelationship between structural measurements and operating controlswhich is well outside the relationship recommended in said U.S. Pat. No.2,822,327 and expressed as a mathematical formula therein.

There has thus been provided an ozone generator structure and method ofoperating it by which the above stated objects are accomplished in athoroughly practical way.

What I claim is:

1. An ozone generator module comprising, a liquid container, an o zo neproducing cell disposed within the said container and comprising a pairof concentric tuthrough the other of said tubular electrodes, one of theliquids being a non-conductive liquid.

2. The ozone generator module claimed in claim 1 in which the innerelectrode of the concentric tubular electrodes is a metal tube and theouter electrode is a metal coating on the outer surface of thedielectric tube.

3. The ozone generator module claimed in claim 1 comprising a pluralityof said ozone producing cells disposed in said container and spacedapart from one another and from the container side wall so that a liquidcoolant disposed within the container will surround the said cells andbe in contact with one of the electrodes of each of the cells.

4. The ozone generator module claimed in claim 1 including valve meansfor controlling the flow of gas comprising oxygen through the cell,other valve means for controlling the flow of dielectric liquid coolant,and means connected in the electric circuit of the module .formonitoring the current drawn by the module, and for controlling saidvalve means to cut out the flow of said gas and said dielectric coolantin case of dielectric tube failure.

U ITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,766,051 Dated October 16, 1973 Inventor(s Joseph Bollyky It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the Abstract, line 1, should read electric Column 1, line 8, aneshould read and Column 1, line 26, before module" change a to read or0011mm 5, line 65, before "generator" change "oxony" ozone Column 7 line36, at the end of the first paragraph following Example 3, change PatentNo. 2,822,317" to 2,822,327

In Example 3, under the headin Ozone output and under the sub-heading O(g. hr. -1

(sq. ft. -l)", the fifth and lowest figure in the column change "31.3"to 31.8

Signed and sealed this 2nd day of April lQYI (SEAL) Attest:

Emma) l i.FLETOl-IER,JR. u. MAnSrIALL 1mm Attesting Officer Commissionerof. Patents FORM pomso (w'GQ) USCOMM-DC 60376-P6 a [L5, GOVERNMENTPRINT'NG OFFICE! 1959 0-366-33 UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 3, 766, 051 Dated October 16 1.973

Inventor(s) s p llyky It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

n 'n In the Aostract, line 1, electlfv should read electric Column 1,line 8, "ane" should read and Column 1, line 26 before "module" change"a" to read or Colwm 5, line "55, before "generator" change "oxony"ozone Column 'Z, line 36, at the end of the first paragraph followingExample 3, change Patent No. 2,822,317" to 2,822,327

In blxarrlple 3, underthe headin "Ozone output" and under thesub-heading "O (g. hr; -1

(Sq. ft. l)", the fifth and lowest figure in the column change "31.3" to31. 3

Signed and sealed this 2nd day of April l97l (SEAL) Attest:

EDWARD M.FLETOHHR,JR. u. mnsmul mum Attesting Officer Commissioner ofPatents FORM PO-105O (IO-69) UscQMM-Dc 5 7 .p 9

* u.sI GOVERNMENT PRINTING OFFICE: 1959 0366334,

1. An ozone generator module comprising, a liquid container, an ozoneproducing cell disposed within the said container and comprising a pairof concentric tubular electrodes connected in a high frequency electriccircuit and separated by a concentrically disposed dielectric tube, thedielectric tube being spaced from one of the said tubular electrodesproviding an electric discharge zone, the distance between the tubesdefining the discharge zone being uniform to within a tolerance of + OR0.017 of an inch throughout the said zone, means for flowing a gascomprising oxygen through the discharge zone, means for flowing a liquidcoolant through said liquid container against a face of one of saidelectrodes, and means for flowing a liquid coolant through the other ofsaid tubular electrodes, one of the liquids being a non-conductiveliquid.
 2. The ozone generator module claimed in claim 1 in which theinner electrode of the concentric tubular electrodes is a metal tube andthe outer electrode is a metal coating on the outer surface of thedielectric tube.
 3. The ozone generator module claimed in claim 1comprising a plurality of said ozone producing cells disposed in saidcontainer and spaced apart from one another and from the container sidewall so that a liquid coolant disposed within the container willsurround the said cells and be in contact with one of the electrodes ofeach of the cells.
 4. The ozone generator module claimed in claim 1including valve means for controlling the flow of gas comprising oxygenthrough the cell, other valve means for controlling the flow ofdielectric liquid coolant, and means connected in the electric circuitof the module for monitoring the current drawn by the module, and forcontrolling said valve means to cut out the flow of said gas and saiddielectric coolant in case of dielectric tube failure.